OCR A2 CHEMISTRY F324 and F325- 14th and 22nd June 2016- OFFICIAL THREAD

dont think like that! just know that each and every single one of us is feeling that way! dont stress, try your best and forget the rest! 😊

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Reply 862

Original post by ranz

guys how are we supposed to know where the double bond is in the structure?!i put it randomly anywhere but in the ms they wanted a specific structure

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It says F is an amino acid, so consider the general formula of an amino acid: http://www.mrothery.co.uk/images/aa.GIF
If E is oxidised to an amino acid by Tollens, that means an ALDEHYDE group is being oxidised to a CARBOXYLIC ACID group :smile:

One carbon must be bonded to an NH2, a COOH, an H and a R group (for F) - hence the only thing you can change is the R group and the double bond must be in the R group. If there is no double bond, it wont fit the molecular formula it gives

(edited 7 years ago)

Reply 863

Serine Soul

18

Original post by AqsaMx

How would you form a carboxylic acid from its salt?

How would you form a 'normal' acid from it's salt? :smile:

(Can you even form an acid from it's salt....)

(edited 7 years ago)

Reply 864

yoda123

15

legit hate chemistry rn :[

Reply 865

AqsaMx

Original post by Serine Soul

How would you form a 'normal' acid from it's salt? :smile:

(Can you even form an acid from it's salt....)

I don't know if this is right but for example CH3COO-Na + HCl > CH3COOH + NaCl? Is this right?

I think you can, my teacher gave it as a set of questions

Reply 866

username986184

Hey! I'll not have that kind of talk!

Reply 867

Serine Soul

18

Original post by AqsaMx

I don't know if this is right but for example CH3COO-Na + HCl > CH3COOH + NaCl? Is this right?

I think you can, my teacher gave it as a set of questions

Ah yes of course!

Reply 868

username1271026

what do you guys think is gonna come up for the NMR imagine if they ask us to draw one- bye

Reply 869

pineneedles

14

You'll be okay, there's loads of people here who will help you with anything you're stuck on. I know I start feeling like that when I've been doing too much work, maybe you need to take a break and relax a bit, just completely forget about the exam for a couple of hours and do something you like. It always does me a world of good.

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Reply 870

ranz

Original post by itsConnor_

It says F is an amino acid, so consider the general formula of an amino acid: http://www.mrothery.co.uk/images/aa.GIF
If E is oxidised to an amino acid by Tollens, that means an ALDEHYDE group is being oxidised to a CARBOXYLIC ACID group :smile:

One carbon must be bonded to an NH2, a COOH, an H and a R group (for F) - hence the only thing you can change is the R group and the double bond must be in the R group. If there is no double bond, it wont fit the molecular formula it gives

thank h soo much! tbh i didnt even think about it being an amino acid, i totally overlooked that and focused more on it being an optical isomer

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Reply 871

ranz

ImageUploadedByStudent Room1465763175.471769.jpg

guys how would one identify the final strucutre out of four isomers? what info would u use to determine that

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Reply 872

RayMasterio

Original post by AqsaMx

Can anyone explain the relative heights question? What's it even asking?

Which paper is this? I want to attempt it myself.

Reply 873

RayMasterio

Original post by ranz

guys how would one identify the final strucutre out of four isomers? what info would u use to determine that

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I can't see the whole question, but look at the number of peaks on the c13 spectrum and look at your isomers and cross out any that have more or less environments than the peak

Reply 874

yoda123

15

How are you structuring your answers for the long answer NMR questions

(edited 7 years ago)

Reply 875

Original post by ranz

guys how would one identify the final strucutre out of four isomers? what info would u use to determine that

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Yeah it's the number of C-13 peaks = no. of carbon environments. Only one of the isomers has 5 carbon environments

Reply 876

marioman

8

Original post by yoda123

How are you structuring your answers for the long answer NMR questions

Table of peaks!

Reply 877

Original post by marioman

Table of peaks!

like this: https://gyazo.com/00189d6d37f578bd4c41e126c744c875 ?

Considering if I should do that.....

Reply 878

marioman

8

Original post by itsConnor_

like this: https://gyazo.com/00189d6d37f578bd4c41e126c744c875 ?

Considering if I should do that.....

Definitely. In that particular question that table alone would score the first 4 marks.

Reply 879